Merge pull request #3013 from pierstitus/pseudocolor_renderer

Rewrite pseudocolor render code to improve speed

python/core/raster/qgscolorrampshader.sip

@@ -26,11 +26,12 @@ class QgsColorRampShader : QgsRasterShaderFunction
       bool operator<( const QgsColorRampShader::ColorRampItem& other ) const;
     };
 
+    /** Supported methods for color interpolation. */
     enum ColorRamp_TYPE
     {
-      INTERPOLATED,
-      DISCRETE,
-      EXACT
+      INTERPOLATED, //!< Interpolates the color between two class breaks linearly.
+      DISCRETE,     //!< Assigns the color of the higher class for every pixel between two class breaks.
+      EXACT         //!< Assigns the color of the exact matching value in the color ramp item list
     };
 
     /** \brief Get the custom colormap*/
@@ -42,7 +43,9 @@ class QgsColorRampShader : QgsRasterShaderFunction
     /** \brief Get the color ramp type as a string */
     QString colorRampTypeAsQString();
 
-    /** \brief Get the maximum size the color cache can be*/
+    /** \brief Get the maximum size the color cache can be
+     * @deprecated will be removed in QGIS 3.0. Color cache is not used anymore.
+     */
     int maximumColorCacheSize();
 
     /** \brief Set custom colormap */
@@ -54,7 +57,9 @@ class QgsColorRampShader : QgsRasterShaderFunction
     /** \brief Set the color ramp type*/
     void setColorRampType( const QString& theType );
 
-    /** \brief Set the maximum size the color cache can be */
+    /** \brief Set the maximum size the color cache can be
+     * @deprecated will be removed in QGIS 3.0. Color cache is not used anymore.
+     */
     void setMaximumColorCacheSize( int theSize );
 
     /** \brief Generates and new RGB value based on one input value */